/*
 *  Licensed to the Apache Software Foundation (ASF) under one or more
 *  contributor license agreements.  See the NOTICE file distributed with
 *  this work for additional information regarding copyright ownership.
 *  The ASF licenses this file to You under the Apache License, Version 2.0
 *  (the "License"); you may not use this file except in compliance with
 *  the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 */

/**
 * @author Alexander Y. Kleymenov
 */

package org.apache.harmony.security.x509;

import java.util.Arrays;

import org.apache.harmony.security.asn1.ASN1Any;
import org.apache.harmony.security.asn1.ASN1Oid;
import org.apache.harmony.security.asn1.ASN1Sequence;
import org.apache.harmony.security.asn1.ASN1Type;
import org.apache.harmony.security.asn1.BerInputStream;
import org.apache.harmony.security.asn1.ObjectIdentifier;
import org.apache.harmony.security.utils.AlgNameMapper;

/**
 * The class encapsulates the ASN.1 DER encoding/decoding work with the
 * Algorithm Identifier which is a part of X.509 certificate (as specified in
 * RFC 3280 - Internet X.509 Public Key Infrastructure. Certificate and
 * Certificate Revocation List (CRL) Profile.
 * http://www.ietf.org/rfc/rfc3280.txt):
 * 
 * <pre>
 *  AlgorithmIdentifier ::= SEQUENCE {
 *      algorithm OBJECT IDENTIFIER,
 *      parameters ANY DEFINED BY algorithm OPTIONAL 
 *  }
 * </pre>
 */
public class AlgorithmIdentifier {

	// the value of algorithm field
	private final String algorithm;
	// the name of the algorithm
	private String algorithmName;
	// the value of parameters field
	private final byte[] parameters;
	// the encoding of AlgorithmIdentifier value
	private byte[] encoding;

	/**
	 * Custom AlgorithmIdentifier DER encoder/decoder
	 */
	public static final ASN1Sequence ASN1 = new ASN1Sequence(new ASN1Type[] {
			ASN1Oid.getInstance(), ASN1Any.getInstance() }) {
		{
			setOptional(1); // parameters are optional
		}

		@Override
		protected Object getDecodedObject(BerInputStream in) {
			final Object[] values = (Object[]) in.content;
			return new AlgorithmIdentifier(
					ObjectIdentifier.toString((int[]) values[0]),
					(byte[]) values[1]);
		}

		@Override
		protected void getValues(Object object, Object[] values) {

			final AlgorithmIdentifier aID = (AlgorithmIdentifier) object;

			values[0] = ObjectIdentifier.toIntArray(aID.getAlgorithm());
			values[1] = aID.getParameters();
		}
	};

	/**
	 * TODO
	 * 
	 * @param algorithm
	 *            : String
	 */
	public AlgorithmIdentifier(String algorithm) {
		this(algorithm, null, null);
	}

	/**
	 * TODO
	 * 
	 * @param algorithm
	 *            : String
	 * @param parameters
	 *            : byte[]
	 */
	public AlgorithmIdentifier(String algorithm, byte[] parameters) {
		this(algorithm, parameters, null);
	}

	//
	// TODO
	// @param algorithm: String
	// @param parameters: byte[]
	// @param encoding: byte[]
	//
	private AlgorithmIdentifier(String algorithm, byte[] parameters,
			byte[] encoding) {
		this.algorithm = algorithm;
		this.parameters = parameters;
		this.encoding = encoding;
	}

	/**
	 * Places the string representation into the StringBuffer object.
	 */
	public void dumpValue(StringBuffer buffer) {
		buffer.append(getAlgorithmName());
		if (parameters == null) {
			buffer.append(", no params, "); //$NON-NLS-1$
		} else {
			buffer.append(", params unparsed, "); //$NON-NLS-1$
		}
		buffer.append("OID = "); //$NON-NLS-1$
		buffer.append(getAlgorithm());
	}

	@Override
	public boolean equals(Object ai) {
		if (!(ai instanceof AlgorithmIdentifier)) {
			return false;
		}
		final AlgorithmIdentifier algid = (AlgorithmIdentifier) ai;
		return (algorithm.equals(algid.algorithm))
				&& ((parameters == null) ? algid.parameters == null : Arrays
						.equals(parameters, algid.parameters));
	}

	/**
	 * Returns the value of algorithm field of the structure.
	 * 
	 * @return algorithm
	 */
	public String getAlgorithm() {
		return algorithm;
	}

	/**
	 * Returns the name of the algorithm corresponding to its OID. If there is
	 * no the such correspondence, algorithm OID is returned.
	 * 
	 * @return algorithm
	 */
	public String getAlgorithmName() {
		if (algorithmName == null) {
			algorithmName = AlgNameMapper.map2AlgName(algorithm);
			if (algorithmName == null) {
				algorithmName = algorithm;
			}
		}
		return algorithmName;
	}

	/**
	 * Returns ASN.1 encoded form of this X.509 AlgorithmIdentifier value.
	 * 
	 * @return a byte array containing ASN.1 encode form.
	 */
	public byte[] getEncoded() {
		if (encoding == null) {
			encoding = ASN1.encode(this);
		}
		return encoding;
	}

	/**
	 * Returns the value of parameters field of the structure.
	 * 
	 * @return parameters
	 */
	public byte[] getParameters() {
		return parameters;
	}

	@Override
	public int hashCode() {
		return algorithm.hashCode() * 37
				+ (parameters != null ? parameters.hashCode() : 0);
	}

}
